The issue centres around PageRank -- the way Google measures and assigns trustworthiness and influence to sites. Links from sites with a high PageRank will increase the PageRank of the site being linked to as the algorithm interprets these links as votes of confidence. By buying links on sites with a high PageRank, an organisation could theoretically manipulate their own PageRank to appear higher in the search engine results pages.

To prevent manipulation, advertorial content is supposed to use a "no follow" attribute which tells Google not to use that link as part of the PageRank calculation. Failure to use the no follow attribute (i.e. selling PageRank) has a variety of different punishments if Google notices including "lower PageRank in the Google Toolbar, lower rankings, or in an extreme case, removal from Google's search results."

Advertisement

According to David Naylor, head of SEO marketing at Bronco, the disappearance of Interflora is likely to be the result of an aggressive advertorial-heavy campaign by the brand in the run up to Valentine's Day and ties in with the sudden decrease in PageRank across dozens of regional newspapers and a handful of nationals who ran the ads.

Many of the publications have seen their ranking drop to zero which Naylor suggests is a punishment for link selling. Interflora declined to comment but its UK site appears to have received the extreme case punishment: being removed from Google's search results altogether. "In January, Interflora, in order to get ready for Valentine's Day, paid newspapers to run stories which were only there to get links to improve their Google ranking," said Naylor in an interview with Computer Weekly. "Google found out and went ballistic."

A representative for Google also declined to comment, but linked to a recent post by engineer Matt Cutts on the company's official blog. The post appears to address the issue without naming specific cases. "Selling links (or entire advertorial pages with embedded links) that pass PageRank violates our quality guidelines, and Google does take action on such violations," reads the post. "The consequences for a linkselling site start with losing trust in Google's search results, as well as reduction of the site's visible PageRank in the Google Toolbar. The consequences can also include lower rankings for that site in Google's search results."